The present invention relates to a sound suppressor and flash attenuator for shotguns and to a method of making the same.
Silencers for firearms are well known in the art and are typically designed for use with rifles and pistols. Heretofore, many different designs have been proposed and manufactured for firearms that use single projectiles, that is, conventional one-piece bullets, the discharge velocities of which are either supersonic or subsonic. Supersonic projectiles typically require silencers with expansion chambers serially disposed inside a gas tight housing along the path of travel of the bullet beyond the firearm muzzle to contain and allow expansion of the gaseous propellant charge and thereby reduce the expansion noise and often the visible flash from the burning propellant. Such expansion chambers usually include baffles arranged more or less transversely to the firearm bore, the spaces between them providing the required expansion chamber volumes.
The central bore of the silencer provided for passage of the projectile is somewhat larger than the projectile diameter to avoid damage to the silencer in the event of a deflection in the path of the projectile. Typically, the tighter the clearance between the silencer bore and the projectile diameter, the greater the noise attenuation achieved. However, attenuation must be balanced against manufacturing tolerances of the silencer, to avoid internal collisions with the projectile discharged from the muzzle.
Ported barrel silencer designs perform better where gasses and projectile velocities are near or below the speed of sound and total gas volumes are relatively low. These designs frequently depend on turbulence chambers and different density damping materials to enhance turbulence. Such designs are well proven, especially in small caliber firearms. These designs normally comprise a jacket tube and inner dividers composed of screen mesh, sometimes attached by a screw thread fitting, or integrally formed with a ported barrel of reduced outer diameter, with layers of screen mesh rolled around the ported section. Many of the designs use compliant, washer-like xe2x80x9cwipersxe2x80x9d which have a central hole for passage of the projectile that has a smaller diameter than the actual diameter of the projectile. See, for example, U.S. Pat. No. 4,974,489. This arrangement provides momentary gas sealing during the passage of the projectile through the series of wipers and chambers. While such designs are effective silencer/suppressors, the combination of the rigid projectile and hot gasses wearing on the compliant wipers results in a relatively short life of the silencer components. Replacement is required, in some cases, in a few as thirty firings.
In most designs of silencers/suppressors, the solid projectile is driven through or past chambers or compliant wipers, and gasses are stripped away and delayed by various mechanisms. Examples of such silencers/suppressors are disclosed in U.S. Pat. Nos. 1,482,805; 4,576,083; 4,588,043; 4,928,573; 5,078,043; 5,136,923; and 5,164,535.
Shotguns have never been easily quieted, due to the problem of the multipart projectiles composed of wads, cards, disks, and loose shot separating in the silencer body, in designs where the projectile flies free. The standard solution for shotgun silencing has been to utilize a ported barrel to contain the shot column and surround the barrel with a layer of material to cause turbulence in the trapped gasses, and delay their release back into the barrel after discharge of the projectile. Shotguns deliver their projectiles and gasses at supersonic speeds. Therefore, silencer designs more suited for sonic and subsonic projectiles are not particularly successful when used on shotguns. Nor are baffle-type silencer designs suitable for shotguns. Lack of safe containment of the shot and wad mass flying freely in the baffle section precludes close clearances. With greater projectile to baffle clearance, attenuation is very poor. U.S. Pat. No. 5,315,914 describes some of the problems associated with shotgun silencing and discloses one prior art solution to shotgun silencing.
It would be desirable to employ techniques for silencing shotguns that are consistent with existing technology for silencing single projectile firearms. The adoption of new shotgun ammunition technology makes possible the silencer/suppressor of the present invention.
The present silencer/suppressor invention has been specifically designed to attenuate the flash and blast of a shotgun firearm. An additional benefit of the invention is recoil reduction owing to the large interior surface area against which the muzzle gasses act in the forward direction.
The circumstance that makes possible the effectiveness of the present invention is the nearly universal adoption by modem shotgun ammunition manufacturers of a high-density polyethylene shot cup and wad assembly. The shot cup of such ammunition is designed to contain the shot during its passage down the bore of the barrel and to cushion the shot against deformation because of contact with the barrel wall. To effect easier loading, the filler wads and overpowder gas seal are made integral with the shot cup. In some designs, the shot holding cup portion of the wad assembly is slit longitudinally so as to open in a petal-like manner upon exit of the wad assembly from the shotgun muzzle. Therefore, until the wad assembly/projectile exits from the muzzle, it exists as a compliant, somewhat elongated projectile.
Some typical examples of shotgun ammunition that are suitable for use with the silencer/suppressor of the present invention include: Federal 12 ga shells loaded with the xe2x80x9c12sxe2x80x9d series plastic wads and Federal sabotted slugs; Remington 12 ga shot shells loaded with the xe2x80x9cPower Pistonxe2x80x9d wad and Remington sabotted slugs; Winchester shot shells using the WAA12F114 heavy load wad; Brenneke 12 ga slugs with attached wad; any specialty 12 ga shot shells with unitized wads loaded by Choke Mfg.; handloaded specialty 12 ga shells loaded with unitized wads known as xe2x80x9cLBCxe2x80x9d or xe2x80x9cRanger Plusxe2x80x9d from Ballistic Products Inc.; and specialty police door-breaching shot shells with powdered metal frangible slugs. It should be understood that the foregoing listing of suitable shotgun ammunition does not include all presently available shotgun ammunition that will function properly with the silencer/suppressor of the present invention. In addition, of course, newly developed shotgun ammunition may also be suitable for use with the silencer/suppressor of the present invention.
The present invention takes advantage of the foregoing features of modem shotgun ammunition in the following manner. First, the compliant nature of the wad assembly/projectile permits the use of non-compliant or non-resilient wad guides or wipes along the projectile bore, without the need for clearance beyond the bore diameter of the shotgun barrel itself. This is the converse of the conventional compliant seal or wipe and rigid projectile combination for gas sealing during projectile passage through a silencer that has been used in many previous designs.
Secondly, by spacing the guides and their mounting baffles close enough to one another in the axial direction, the need for a continuous barrel through the baffles is eliminated allowing the use of a silencer design more suited to the supersonic nature of a shotgun discharge. The wad assembly spans at least two guides at all times, and engages three guides for most of its travel through the silencer baffles. This arrangement provides excellent sealing and maintains the wad assembly in a closed, single-projectile-like condition. Accordingly, the attenuation level for the silencer of the present invention is very high and is comparable to that of the better silencers available for single projectile firearms.
Thirdly, because the traveling compliant seal formed by the wad assembly is replaced with every shot, the interior components of the silencer of the present invention have a long life when compared with conventional sealing wiper designs. Maintenance is simplified to rinsing out carbon and errant power grains from the silencer interior. The use of a lubricating coolant or coupling fluid also reduces wear of the guide bores or wipes from passage of the projectile.
Previous baffle cone silencer designs have been expensive because of the high cost of the stamping dies necessary for manufacturing the inner partitions. Other prior art designs use complicated machined parts with complex angle cuts and close tolerances. The present invention has been simplified and optimized for inexpensive manufacture on screw machines, robotic lathes and high volume computer-controlled machines. Stock material sizes can be utilized for all components.
With the foregoing and other objectives, features and advantages of the invention that will become hereinafter apparent, the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and the several views illustrated in the drawings attached hereto.